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Deep-Sea Mining—Bonanza or Boondoggle?

The ocean floor is rich with valuable minerals, but mining them could disrupt fragile ecosystems teeming with life.

ByBrooke JarvisNOVA NextNOVA Next
A fish hovers by a forest of tubeworms at a hydrothermal vent on the ocean floor.© WGBH Educational Foundation

Here on Earth, deep beneath the ocean’s surface, you’ll find an alien world.

It’s a place where seawater may be as acidic as vinegar and boiling hot, yet under such intense pressure that it’s neither a liquid nor a gas, but something in between. It’s populated by ten-foot-long tubeworms, swarms of eyeless shrimp, and hairy, fist-size snails, all of which thrive on chemicals that would kill most species. Our most basic understanding of life doesn’t apply here: energy doesn’t come from photosynthesis but chemosynthesis, a process thought to be science fiction just forty years ago.

This is the world of deep sea hydrothermal vents, geothermally active fissures that are often miles beneath the ocean’s surface. It’s also, improbably, the next frontier of the mining industry—the future home of what some are calling a new gold rush.

Hydrothermal vents create rock formations called seafloor massive sulfides that contain a fortune in minerals, if only we could get them to the surface. They range from gold and copper to rare earth elements and platinum group metals, all coveted for their role in producing consumer electronics, defense systems, and even green energy innovations.

No, your phone doesn’t contain any minerals from hydrothermal vents just yet—the world’s first deep-sea mining project, due to start this spring, was shelved due to a contract dispute. But dozens of exploratory leases have been issued or are in process. Companies are prospecting all over the world, from the Atlantic and Pacific to the Indian Ocean and the Red Sea. As you read this, mining companies are drawing up plans to harvest the minerals using remotely operated vehicles to grind rocks to a slurry before they’re piped to barges on the surface. Many observers agree it’s only a matter of time until the first vent site is mined.

“It’s the great unknown.”

But they’re also asking how far we’ll go for minerals. Nautilus Minerals, the first company to secure a license to mine a hydrothermal vent, describes itself on its website as “following the lead by the offshore oil and gas industry to tap vast offshore resources.” Deep sea mining opponents find that comparison all too apt. Some compare vent mining to fracking, Arctic drilling, or tar sands development—a sign we’re going to new and ever more extreme lengths for minerals as we do for energy.

Indeed, it would be hard to go further. “These are genuinely frontier ecosystems,” says Andrew Thaler, who studies the population dynamics of vent ecosystems at the Duke University Marine Lab. “With the exception of maybe deep sea canyons, they’re the hardest ecosystems that we can possibly get to.” There’s a lot that we don’t yet know about how vent communities work, how they’ll be affected by mining, or even how we’ll police this new industry. “It’s the great unknown,” Thaler says.

Yet someday soon, the products of this alien world will likely be entering our homes and shopping malls. Researchers and regulators are racing to understand what we’re getting ourselves into.

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An Underwater Bonanza?

We’ve been talking about mining the deep sea for decades. The first targets, in the 1960s and 1970s, were polymetallic nodules, billiard ball-sized chunks containing nickel, manganese, cobalt, copper, and iron that litter the abyssal plains of the deep ocean. Though a number of mining companies explored ways to harvest the nodules—essentially vacuuming them up off the seafloor—nodule mining never became commercially viable. But recently, the International Seabed Authority (ISA), created under the Law of the Sea Convention to manage seabed mining in international waters, announced that it was seeing “an unprecedented surge” of interest from mining companies. It expects leases for nodule mining to become available in 2016.

polymetallic nodule
Early deep-sea mining proposals considered vacuuming polymetallic nodules like this one off the sea floor.

Advancing mining technology and spiking prices for minerals have reignited interest in deep sea mining. But much of the attention has shifted to hydrothermal vents, where minerals are more densely concentrated than in nodules and which are generally found closer to the ocean’s surface than nodules—though still far deeper than we’ve ever mined before.

Companies are also beginning to eye another underwater formation: the cobalt-rich crusts of underwater volcanoes, also known as seamounts. Mining would mean using robots to scrape off their sides—a kind of underwater mountaintop removal. With these techniques—and others—mining may meet with some resistance from the fishing industry. Seamounts are havens for fish in the open ocean, and many of the shallower ones are already exploited as fisheries.

Davidson Seamount
At a depth of 2,669 m (8,757 ft), black coral, primnoid coral, and feather stars cover this part of the Davidson Seamount off the coast of California.

Despite the challenges, deep sea mining has some potential benefits over terrestrial mining. Because vent mineral deposits are so much younger than most deposits found on land, they’ve had less time to degrade or disperse. For example, says Maurice Tivey, a geophysicist based at Woods Hole Oceanographic Institution, at vent sites “you get gold concentrations up to 15 parts per million. On land, you’d mine at between one and five parts per million.” The minerals are often much closer to the surface, so operations have to dig and displace less rock, meaning a smaller footprint and fewer carbon emissions. Seabed mining infrastructure is both moveable and reusable, unlike roads and buildings often left behind at abandoned mines on land. And no residents will be directly displaced by mining.

But the certainties stop there. The difficulty of reaching deep sea vents, together with the fact that they were only discovered forty years ago, means there’s a lot we still don’t know about how vent ecosystems work or how mining them will affect the larger ocean.

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“We’ve only just scratched the surface looking for these vent systems and trying to find new life forms,” Tivey says, who worries that mining companies’ greater resources will allow them to get to vent sites before scientists do. “It’s too soon for us to understand what exactly all the feedbacks are.”

A Question of Scale

“The biological effects of mining are pretty clear,” says Jeff Ardron, a senior fellow with the Institute for Advanced Sustainability Studies who focuses on how we govern the areas of the ocean beyond national jurisdiction. “In the area where you mine, everything is killed. Anything that’s alive in the path of these operations isn’t alive anymore.”

That’s somewhat less apocalyptic than it sounds. Most vent ecosystems are extremely dynamic—the vents themselves are constantly opening and closing and reopening somewhere else, meaning that the specific communities they support last, in general, 12 to 100 years. (Vents on slow-spreading ridges are an exception.) The animal species that populate them survive by spreading progeny far and wide to colonize fresh vents. The question is whether mining will introduce more variability than the ecosystem can handle. If mining is in a limited area and there are enough healthy vent communities nearby for repopulation, it may not.

“It’s a question of scale,” Thaler says. “If it’s one deep sea mine done once, or a few spread out over a long period of time, it will have a very different effect than if it’s a sustained, continuous operation that’s constantly putting pressure on the same vent system.” But it’s hard to be sure, in part because each vent area is so unique.

“It’s not something you can really infer; you have to go in and do the experiment, and doing the experiment is kind of a scary thought,” he continues. “The only way to figure out how the system changes in response to disturbance is to disturb the system.”

Iridigorgia pourtalesii

There are other concerns beyond direct destruction. Sediment is a major one. Mining will mix tons of rock and debris into the seawater. Sediment could blanket a large area, harming vents that haven’t been mined and making it difficult for animals to repopulate destroyed areas once mining is over. It may also have an impact beyond the vents, too, in other parts of the deep sea that are usually extremely stable. “Once you start impacting the background deep sea, then you’re affecting an ecosystem that doesn’t experience disturbance almost ever,” Thaler says. “So those species probably can’t cope.”

Ardron worries about the long-term impacts of early mistakes, arguing that new industries often wreak the most damage in their earliest days, when companies deep in speculative debt cut corners rather than prioritize environmental protection. “If this approach is taken in the deep sea—where we kind of let things be a little dirtier at the beginning and then clean it up—things don’t recover, things don’t recycle in the deep sea in the way that they do in the world that we’re familiar with. It’s a centuries to millennia time scale down there.”

Eel in deep coral

Tivey has additional concerns: The slurry piped up from the seafloor will be highly acidic, full of ground-up metals whose increased surface area will make them more reactive, capable of forming hydrogen sulfide or sulfuric acid. Should a barge sink, a pipe come lose, or a spill occur in shallow water before the byproduct can be piped back to the seabed it came from, “it could acidify a whole reef,” he says. “This stuff is not nice.”

The Deep Sea Mining Campaign, an Australia-based NGO that advocates for communities near proposed deep sea mining sites, has also raised concerns that heavy metals and other toxins could remain in the water after ore is removed; even if it is successfully piped back to the seafloor, the NGO is concerned that upwelling water could harm fish and residents who live near mining sites.

Policing the Deep Sea

It was the prospect of deep sea mining that prompted the Law of the Sea Convention, an effort to regulate marine resources it calls “the common heritage of all mankind.” Concluded in 1982 and ratified in 1994, the Convention set up the ISA to issue mining leases and regulate how minerals and other resources outside of national economic zones can be harvested. (Mining within territorial or archipelagic waters or Economic Exclusive Zones, which extend for 200 miles off of coastlines, is within national jurisdiction. Island nations are already scrambling to figure out how to oversee and profit from mining projects. For signatories to the Law of the Sea, the ISA’s regime will be a guidepost.)

“Right now, we’re flying in the dark.”

But the current system has a number of unresolved issues, Ardron says. The ISA doesn’t coordinate with the international bodies that oversee other ocean industries, such as fishing and shipping. Without communication, it will be hard to know when areas are being overtaxed. Likewise, the ISA’s current method for protecting what it calls “Areas of Particular Environmental Interest” is not proactive: first mining leases are assigned, then certain areas outside those leases are protected. “Right now, we’re flying in the dark,” Ardron says. “We don’t know if these leases are in ecologically important places or not—and it’s too late by the time they’re handed out.”

There are also concerns about the transparency of the approval process—“generally we don’t know what leases are up for discussion until they’ve already been approved,” Ardron points out—as well as about how future infractions will be dealt with. Because no projects have gone into production yet, he argues it’s not too late to push for stronger reporting, transparency, and compliance guarantees: “The door hasn’t closed yet.”

But with the rush for mining leases on, it is beginning to close. And at stake is a strange world we have only barely begun to understand.

It can be difficult, Thaler says, to explain his interest in deep sea vents to non-scientists. But he tries: “Hydrothermal vents are pretty much the closest thing we can get to alien life while still being on earth,” he says. “They’re utterly unique in terms of the ecology, biology, and physiology of these organisms. We discovered a whole new way of being alive when we found hydrothermal vents. Every time we discover a new vent site we discover a new species—sometimes totally different from anything we’ve seen before.”

The oceans, Ardron points out, are already under a lot of pressure: intensified fishing, deep water oil and gas drilling, ocean acidification, changes in temperature and circulation, and more. “The ocean is already, in some cases, in trouble, but in all cases under a lot of stress,” he says. “And here comes another one.”

Photo credits: NOAA, Parent Géry (CC-SA) , and USGS

Funding for NOVA Next is provided by the Eleanor and Howard Morgan Family Foundation.

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